Sorption And Immobilization Of Low-Concentration PAHs In Water By HDTMA Modified Clays

In this research, the current situation of pollution and remediation of polycyclic aromatic hydrocarbons (PAHs) in surface sediments, and the application and potential prospects of organoclay were reviewed at first. Based on the principle of in-situ treatment of sediments, organoclay was chosen as sorbant and was used to adsorb low-concentration PAHs in water. The effectiveness of organoclay for the controlling of PAHs pollution in pore water was further studied. The results provide theoretical fundations for the application of organoclay in in-situ treatment of polluted sediments.The natural clays were modified with hexadecyltrimethylammonium bromide (HDTMA-Br), tetramethylammonium bromide (TMA-Br) and polyethylene glycol 400 (PEG 400) respectively. The sorption of PAHs (phenanthrene and anthracene) in water by these organoclays was studied. The stability of the sorption and the effect of the amounts of organoclays on the sorption capacities were also investigated. It was concluded that the adsorption isotherm curves for phenanthrene on three different organoclays were all dished, which indicated that sorption was the actions of both partition and solvent effect. On the other hand, the adsorpotion isotherm of anthracene was linear, which was ascribed to the action of partition. For both phenanthrene and anthracene, the order of the adsorption quantity of organoclay was HDTMA-modified clay > PEG-modified clay >TMA-modified clay.The capability and mechanism of adsorbing the mixture of phenanthrene and anthracene from water by organoclay were studied. According to the above conclusion, HDTMA-Br was chosen as the surfactant for modifying the nature clay. The results of adsorption experiments showed that the adsorption isotherm curves for phenanthrene, anthracene and their mixture in mixed solution on HDTMA-modified clay were all linear and it indicated that the sorption behaviors were affected by the action of partition. Furthermore, the sorption for single phenanthrene and single anthracene on organoclay and the sorption for the mixture of phenanthrene and anthracene were contrasted, and the result indicated that the total adsorption capacity of organoclay increased largely and was almost the sum of the capacities of organoclay adsorbing single phenanthrene and single anthracene.The immobilization of PAHs by organoclay in pore water was further testified. The study showed that the PAHs of sediment pore water was adsorped completely by HDTMA-modified clay. It proved that the PAHs of sediment pore water could be immobilized by HDTMA-modified clay effectively.